The overall objective of this project concerns the synthesis and metabolic studies of a relatively unexplored class of nucleosides -carbocyclic nucleosides. Synthetic carbocyclic nucleosides will be produced and a study of the molecular requirements for metabolic activation and inactivation will provide a basis for further rational design of metabolic inhibitors. The compounds prepared in this project will exhibit antitumor and/or antiviral activity by inhibiting the synthesis of nucleic acids.